Can't play downloaded games from USB

I downloaded a few games and used WBFS manag. 3 to transfer them on my USB, but at the end of the process, the size of each game shrink considerably (from 3 or 4GB to 0.5 or .06GB) on the usb card, then when i try to play them on my wii, it gives me an error message.
Ps: i unzip each time and use the .iso file to save the games.
Thanks for ur help

1 User Says Thank You dangerd187 For This Useful Post

yes i'm using a SD card. As the following reply said, games can be reduced to 2 or 3 GB, but in my case they go down to 0.6 GB, which i believee for a game is far to small. Am i extracting the wrong file ? there is only one .iso file anyway, can't be that

I found the reason I couldn't play the downloaded games: My mistake was that i was trying to open them using directely The usb loader from the wii menu. What i should have done was to open my NeoGamma in the homebrew channel, then scroll down to "Load games from : <DVD>, using the right-direction control on the remote, change this to "load games from: <USB>, scroll up and press A. Et voila, all the games on the usb appear.
It was too easy!! Sorry for the nuisance guys, i'm really not good with Hi-tech.
Thanks again everyone